The human heart consists of a total of four chambers, the right atrium, the right ventricle, the left ventricle and the left atrium. Deoxygenated blood is pumped into the right atrium through the superior vena cava and the inferior vena cava and from there the deoxygenated blood passes through a first cardiac valve, the tricuspid valve, into the right ventricle. From the right ventricle, the deoxygenated blood passes through a second cardiac valve, the pulmonary valve, into the pulmonary artery. When the blood has absorbed oxygen in the lungs, it flows through the pulmonary veins to the left atrium of the heart. Then, the oxygenated blood passes through a third cardiac valve, the mitral valve, into the left ventricle. From there, the oxygenated blood passes through a fourth cardiac valve, the aortic valve, into the aorta from where it supplies all the human organs inter alia with oxygen.
As valves, the cardiac valves ensure that the blood only flows in one direction when pumped by the cardiac muscle. Stenotic or leaking cardiac valves present an acute hazard. In the first case, insufficient blood flows through the valve in question. In the second case, the valve function is impaired and too much blood flows back into the respective region before the cardiac valve structure, for example the left or right ventricle, even though the cardiac valve is closed. Problems with the cardiac valves are, for example, caused by calcareous deposits on the valves, by inflammation of the valves or cardiac muscle or can also be the result of myocardial infarction. Cardiac valve defects are also occasionally congenital.
As a rule, a several cardiac valve defect requires surgical treatment since otherwise there is a risk of permanent damage to the cardiac muscle resulting in gradually further reduced pump function, reduced physical capacity and ultimately greatly shortened life expectancy. Cardiac valve surgery is usually performed with an open thorax and arrested heart while a heart-lung machine maintains the circulation artificially. This always entails a certain risk of the patient suffering a stroke, which can be accompanied by impaired motor functions and impaired intellectual faculties.
Alternatively, for several years, it has also been possible to use a minimally invasive catheter-based method known by the acronym TAVI (TAVI=transcatheter aortic valve implantation). With TAVI, cardiac valves are implanted into the beating heart without open surgery. Therefore, there is no longer a need for connection to the heart-lung machine so that the described risk of stroke no longer exists. With a minimally invasive procedure of this kind, there is no need to remove the defective cardiac valve—it is merely pushed toward the side. A prosthesis, i.e. a biological cardiac valve, is now used instead of the old valve. This technique is generally used with particularly endangered patients in whom open surgery would be too risky. In this case, the prosthetic valve is introduced with the aid of a catheter, a thin flexible plastic wire, through the vessels as far as the heart and unfolded at the position of the defective cardiac valve. As a rule, access is either through the inguinal vessels or via the cardiac apex.
However, following the use of the TAVI method, it is not uncommon for paravalvular leaks to occur if the artificial cardiac valve was not inserted in an exactly planar manner into the existing aortic valve or the annulus, i.e. the base of the aortic valve. It is necessary to prevent the occurrence of such leaks since they could result in impairment of left-ventricular function and hemolysis.
To date, leaks of this kind have been sealed via an additional occluding element. However, this requires a further invention. Moreover, there is also a further implant in the region of the cardiac valve in addition to the prosthetic valve.
There are also so-called repositionable prosthetic valves but these are associated with risks with respect to stability in the annulus.